A number of dispensing devices are available for dispensing various types of materials. In many instances, the dispensing device is an assembly that includes a reusable dispenser or applicator and a disposable cartridge. The cartridge contains a quantity of a composition or material to be dispensed and is releasably received in a receptacle of the applicator.
In one type of dispensing devices, that include an applicator and a cartridge, the applicator has a plunger that is advanced by the user during a dispensing operation. Often, the plunger is received in an open end of the cartridge and bears against a piston within the cartridge. As the plunger is advanced to move the piston, the piston expels a quantity of material through a front outlet opening of the cartridge. The cartridge is made from a plastic material.
Dispensing devices with cartridges are often used in the field of dentistry for mixing and dispensing dental compositions of two components, such as impression materials, restoratives, adhesives, cements, etching gels, sealants and the like. The dispensing cartridge of such devices is made from a plastic material and comprises two compartments which are formed by two cylindrical bodies arranged in parallel to each other. Each compartment contains a specific component, usually a base paste and a catalyst paste. These two components are pressed from their respective compartments out into a mixing tip where the required dental material is prepared. The pressure further urges the mixture out of the mixing tip so that the dental professional can use it as desired.
One type of such dispensing devices is an assembly (e.g., the Garant™ dispenser available from 3M ESPE AG) that includes a reusable, hand-operated applicator and a disposable cartridge (e.g., the cartridge for the polyether impression material Permadyne™ Garant™ available from 3M ESPE AG). The two compartments are of the same cylindrical shape and size and are pre-filled with the two components to be mixed and dispensed.
Another type of such dispensing devices is an automatic dispensing system (e.g., Pentamix™ available from 3M ESPE AG) that includes a motor-driven mixing unit and reusable and interchangeable cartridges (e.g., the cartridge for the polyether impression material Impregum™ Penta™H DuoSoft, or the cartridge for the polyether impression material Permadyne™ Penta™, or the cartridge for the vinyl polysiloxane impression material Express™ Penta™H, all available from 3M ESPE AG). These two cylindrical compartments have different diameters, and, in use, each accommodates a disposable foil bag pre-filled with the respective component. The larger compartment usually accommodates the foil bag with the base paste. The smaller compartment usually accommodates the foil bag with the catalyst paste. The mixing unit comprises a chamber for holding the cartridge and two parallel motor-driven plungers designed to plunge into the respective compartments and to exert pressure on the components contained in the foil bags.
Both foil bags comprise a respective cap that fits onto the rim of the respective cylindrical body of the dispensing cartridge. The conventional dispensing cartridge is fully made of plastic material which has to be strong enough to stand the pressure applied by the plungers on the bags during use, and which has to be chemically inert to the aggressive, usually acid chemical character of the pastes. Moreover, the plastic material has to be easy to handle in the injection mould, i.e., low shrinking rate and little ability to form shrink marks. These different requirements are difficult to meet.